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The scientific instrument used to measure noise is the sound level meter. Sound level meters can accurately measure environmental noise levels to within about plus or minus 1 dBA. Various computer models are used to predict environmental noise levels from sources, such as roadways and airports. The accuracy of the predicted models depends upon the distance the receptor is from the noise source. Close to the noise source, the models are accurate to within about plus or minus 1 to 2 dBA. Since the sensitivity to noise increases during the evening and at night -- because excessive noise interferes with the ability to sleep -- 24-hour descriptors have been developed that incorporate artificial noise penalties added to quiet-time noise events. The Community Noise Equivalent Level, CNEL, is a measure of the cumulative noise exposure in a community, with a 5 dB penalty added to evening (7:00 pm - 10:00 pm) and a 10 dB addition to nocturnal (10:00 pm - 7:00 am) noise levels. The Day/Night Average Sound Level, Ld,,, is essentially the same as CNEL, with the exception that the evening time period is dropped and all occurrences during this three-hour period are grouped into the daytime period. REGULATORY CRITERIA The proposed project would be subject to noise-related regulations, plans, and policies established within documents prepared by the City of Pleasanton. These documents are implemented during the environmental review process to limit noise exposure at existing and proposed noise-sensitive land uses. Applicable planning documents include: (1) the City of Pleasanton General Plan: Noise Element, and (2) the City of Pleasanton Noise Ordinance. Regulations, plans, and policies presented within these documents form the basis of the significance criteria used to assess project impacts. City of Pleasanton General Plan Noise Element The City of Pleasanton's General Plan Noise Element sets forth Noise and Land Use Compatibility standards for residential developments. Policies in this Element, which affect the residential land uses adjacent to the project site are: • A 60 dBA Ldn goal is to be applied for single-family residences and a 65 dBA Ldn goal for multi-family residences where outdoor use is a major consideration (e.g., backyards in single-family housing developments and recreation areas in multi-family housing projects). For new residential developments, use the "normally acceptable" designation and text description contained in Table 11-5. • People in front yards can generally tolerate up to 65 dBA Ld,,; if the front yard noise level is greater than this, however, interior noise levels would become a concern. • Indoor noise levels shall not exceed 45 dBA Ld„ in multi-family dwellings or single- family residences. • An exterior increase of more than 4 dBA is considered significant. Page 6